Combine harvester

A threshing portion is one of the components of a combine harvester which are large in energy consumption and easy to jam. When the threshing portion is jammed, a conventional method includes stopping the combine harvester, manually increasing gaps between large concave plates, and taking out superfluous cereals to solve the jam. The invention provides a concave plate gap automatic modulating system which can continuously detect the cereal flow by a single chip microcomputer, modulate gaps between concave plates by a stepping motor on the premise of no shutdown in case of jam, and automatically recover the gaps between the concave plates. The system can automatically clear of trouble about jam in rollers without shutdown, and the efficiency of usage of a harvester can be greatly raised.